Mass Email Professionals have a job to do, and that is to get the emails into INBOXes. To make an email campaign successful, there are things that need to be in place before you hit the send button or it is possible that even though all your emails seemed to go out, many of your emails could be in the SPAM box which is as good as the recipient not getting the email at all. So, in order to increase your effectiveness in getting those emails delivered correctly, there are some guidelines you should follow that will be true for many of the big email providers like Gmail, AOL, and hotmail.
Make sure you have an SPF record in your DNS!
This is the #1 problem why email does not make it to the recipient, and many times you wont even know it. Gmail requires this, and every email sent to it, it makes sure the SPF record is there. At best, it goes into the Spam folder, at worst, it does not make it at all.
Make sure your links in your emails are not IP addresses and that they use port 80 (HTTP)
Many times you can just cut and past a URL not really noticing that the URL is an IP address or that it may even use a non-standard port. These are huge red-flags to recipient email systems. Also, try not to make the "test" part of a hyperlink the same URL. Use real words like, "Click here to see..." or something.
Make sure your subject line is not too "flower-y"
Using all upper case words or lots of punctuation in your subject line can cause a higher spam score. You want to attract attention to your subject but it should be done tactfully. Use some type of useful information that is very specific to the recipient so that you may attract their attention. Just mentioning their name is not good enough, and can sometimes be annoying and look like SPAM. Be specific! Think about what you would click on if you saw your subject line. Getting an email to an INBOX and not having the recipient even open it is a crime! Bad examples of this are:
YOU HAVE TO SEE THIS!
Hello Chris, I think you will like this
It sounds simple, but you would be surprised by how many do this type of thing in the subject. This happens a lot too when the email is not written by a person not using primary language skills or different cultures. I don't mean to be harmful here, but many terms and sayings can be outdated or actually repelling, so make sure you edit things before sending out. Overall, write emails like you were just writing to one person in a normal scenario.